The disclosed embodiments relate to a technology of manufacturing a substrate having flexibility on which an electronic component is mounted.
From the viewpoint of convenience and portability, a display device including an image display unit having flexibility, such as a film liquid crystal display and a flexible organic EL display, attracts attention.
As a body component of such a display device, a flexible display substrate is used. In this flexible display substrate, a flexible substrate (such as a flexible, transparent plastic film) has an image display region for displaying an image and a mounting region where an electronic component (for example, a driver IC) for processing a picture signal of an image display device is mounted. When an electronic component is mounted, a thermosetting anisotropic conductive film is usually disposed in the mounting region, and an electronic component is disposed on the anisotropic conductive film. Then, heating and pressing are generally performed to fix the electronic component. When a plastic film that serves as a substrate is reduced in thickness, or when rigidity is decreased for further enhancing the flexibility of the flexible display substrate, the above-described heating and pressing tend to cause the substrate to be deformed or distorted, leading to deterioration of displayed images.
On the other hand, the field of circuit boards is different from the field of the above-discussed flexible display substrates but is common in terms of the use of a flexible substrate. That is, in the technical field of flexible printed circuit boards, there is a technology of adhering a reinforcing plate (backing plate) to the back surface of an external terminal region formed on the edge of the circuit board. The reinforcing plate on the back surface supports heat or stress applied on the edge so as to prevent distortion or deformation caused when the circuit board is inserted into another component or an electronic component is mounted on the circuit board.
Examples of the above-discussed reinforcing plate specifically include a thermosetting-type reinforcing plate, that is, a thermosetting sheet, as disclosed in Patent Literatures 1 to 3, and an adhesive sheet as disclosed in Patent Literatures 4 and 5.